I've just learned of a new photo editing program that can be used directly in a web browser without any need to download software. Its user interface is practically identical to that of Photoshop, so there's no learning curve for those already familiar with the Adobe software. Best of all, it's available free of charge.
Developed by Ivan Kutskir in the Czech Republic, Photopea appears to share all the most important features available on PS including layers, layer masks, blend modes, brushes, selections and image adjustments.
As far as file formats, it should be possible to open files in the standard formats (jpg, tiff, gif, png, svg, and dng) as well as the proprietary formats psd, xcf, and sketch and then save to the following formats: jpg, psd, png and svg.
It should be noted that Photopea may not work properly, or at all, on older web browsers such as MS IE 11. On the other hand, I encountered no problem at all accessing it on Google Chrome.